Digital in - Voltage?

knebb

Hi,

I have a fan I would like to control by the Neuron digital Output. I got a wirering picture how to connect to a Raspi to control it by PWM.

My question is: In the Neuron Docs it states for the digital Output 5-50V. But Raspi has 3.3V instead of 5V.

How do I connect to my tacho IN signal? Where doe I get power from?

Thanks a lot!

TomasKnot

Hi @knebb!

You will need to use an external source of the proper voltage to drive the fan, with the Neuron performing the PWM function and switching it on and off.

The 5V is not available externally from the Neuron, nor any other power lines, including the 3.3v. Though technically speaking our internal PSU provides 3.3v, 5v as well 24v; however this is not designed for external use.

knebb

@TomasKnot
perhaps I misunderstood you, but you might have seen in the wiring schema I have a proper external voltage for the fan (provided by the 100kR resistor and the Z-diode).

I am asking for the power to drive the transistor (BC547c)- can I connect the "left" par of the transistor to any of the Neuron digital outputs?
Did I get it right the Neuron does not provide any power here and I would have to use an external power supply as shown here.
Would this work now? Or do I need some resistors? Where? Dimension?

0_1525960327818_Schaltung Lüftungssteuerung PWM - Neuron.png

TomasKnot

You can just use our DO instead of the transistor, see the schema below:

If you have trouble with it working, you can try a lower resistor (40k, 22k)

knebb

@TomasKnot said in Digital in - Voltage?:

You can just use our DO instead of the transistor, see the schema below:

Cool, looks really good. I will give it a try. Just one thing I am unsure about.

If you have trouble with it working, you can try a lower resistor (40k, 22k)

The control input has max 10V. If I change Resistor doesn't it change the voltage?

tomas_hora

@knebb said in Digital in - Voltage?:

rol input has max 10V. If I change Resistor doesn't it change the voltage?

If the control input can survive max 10V, then you need to use 10V zener diode (ZD1). The resistor only limits the current to the ZD and DO, the value has to be calculated by you.